Thread monitoring mechanism

Abstract

A thread monitoring mechanism for a thread processing location with a swivel lever which is mounted on a swivel axis and on which a thread guidance roller overrun by the thread that is to be monitored is mounted and which is elastically supported by a supporting member adjustable in accordance with a predetermined thread tension, in which respect the swivel lever has a switching member for interrupting the thread travel and/or for switching-off the thread processing location as soon as the actual thread tension deviates by a specific amount from a predetermined thread tension value, is characterized in that the suporting member is pneumatically supported, in which respect serving for supporting the swivel lever are preferably two supporting members which are supported pneumatically by membranes which have effective membrane surfaces of different sizes.

What is claimed is: 
     
       1. A thread monitoring mechanism adapted for use in a textile machine for sensing variations in tension of traveling thread from a predetermined value for use in controlling the travel of the thread; said mechanism comprising: a housing adapted to be mounted on the textile machine in the path of thread travel;   a swivel lever mounted on said housing for movement about a swivel axis;   a thread guide roller for being engaged by the traveling thread and mounted on said swivel lever for movement thereof under the influence of variations in the tension of the traveling thread from a predetermined value;   switch means adapted to be connected to the textile machine for controlling the travel of the thread;   a switching member carried on said swivel lever for actuation of said switch means upon movement of said swivel lever caused by a variation in the tension of the traveling thread; and   a plurality of support means contacting said swivel lever for providing predetermined support against movement of said swivel lever for providing the predetermined value of thread tension, said support means including multiple pneumatic support means for being individually and selectively pressurized.   
     
     
       2. A thread monitoring mechanism, as set forth in claim 1, in which each of said pneumatic support means includes a piston member engaging said swivel lever, an elastically deformable diaphragm engaging and supporting said piston, and means for supplying pneumatic pressure against said diaphragm for regulating the strength of the support thereof. 
     
     
       3. A thread monitoring mechanism, as set forth in claim 2, in which each of said means for supplying pneumatic pressure comprise means for supplying different partially overlapping ranges of pneumatic pressure. 
     
     
       4. A thread monitoring mechanism, as set forth in claim 2, in which each of said diaphragms have effective diaphragm surfaces of different sizes, and in which each of said means for supplying pneumatic pressure includes a common source of pressure and a common pressure regulator. 
     
     
       5. A thread monitoring mechanism, as set forth in claim 1 or 2, in which said support means further includes a compression spring means of predetermined strength. 
     
     
       6. A thread monitoring mechanism, as set forth in claim 1, in which said swivel lever comprises two lever arms, and in which one lever arm carries said switching member and the other lever arm contacts said support means. 
     
     
       7. A thread monitoring mechanism, as set forth in claim 1 or 6, in which said switch means includes a pin member, and said switching member comprises a fork-shaped member into which said pin member projects. 
     
     
       8. A thread monitoring mechanism, as set forth in claim 1, further including a stop means for selectively engaging said swivel lever to hold the swivel lever in fixed position prior to said mechanism receiving a traveling thread. 
     
     
       9. A thread monitoring mechanism, as set forth in claim 1, further including a pneumatically actuatable thread severing means controlled by actuation of said switch means.